ax88179_178a: add ethtool_op_get_ts_info()

This enables the use of SW timestamping.

ax88179_178a uses the usbnet transmit function usbnet_start_xmit() which
implements software timestamping. ax88179_178a overrides ethtool_ops but
missed to set .get_ts_info. This caused SOF_TIMESTAMPING_TX_SOFTWARE
capability to be not available.

Signed-off-by: Andreas K. Besslein <[e-mail]>
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/usb/ax88179_178a.c

···
 	.nway_reset		= usbnet_nway_reset,
 	.get_link_ksettings	= ax88179_get_link_ksettings,
 	.set_link_ksettings	= ax88179_set_link_ksettings,
+	.get_ts_info		= ethtool_op_get_ts_info,
 };
 
 static void ax88179_set_multicast(struct net_device *net)